Since 1993, Mexican coastal communities such as Puerto Peñasco and Golfo de Santa Clara in Sonora, and San Felipe in Baja California have been connected by the Upper Gulf of California and Colorado River Delta (RBAGC) biosphere reserve. This reserve was created to preserve and protect several endemic species, among them the vaquita marina (Phocoenasinus), a marine mammal, and a fish known as totoaba (Totoaba macdonaldii).The present article reviews and analyzes the social and economic impact of the reserve on small scale fishers in San Felipe in Baja California, considering that the reserve is an institutional arrangement designed for environmental and ecological protection as well as fishing regulation.The analysis focuses on the socioeconomic impact of the reserve's creation on fishing in San Felipe in 1994 and 2002. The main conclusion is that social and economic factors should be considered when designing evaluation and efficiency indicators in order to obtain a successful reserve.